Ships and other floating platforms often roll and pitch so severely when on station at sea, for example, in oil drilling and pipe-laying operations, that operations must be discontinued. Many prior systems for reducing the roll and pitch motions of vessels have attempted in various ways to damp these motions. One prior system proposes a series of interconnected tanks and airblower to lengthen the natural periods of these motions by reducing the righting moment of the vessel. See, for example, U.S. patent application Ser. No. 787,756, entitled, "System for Stabilizing a Floating Vessel" filed on Apr. 15, 1977, by Gunnar B. Bergman now U.S. Pat. No. 4,140,074. However, apparatus for controlled reduction of righting moment and correspondingly lengthened roll and pitch periods of a vessel constructed according to the present invention, is less costly than prior art systems. Furthermore, the present invention requires less space on deck and within the hull of the vessel on which it is installed, thus leaving more space available for equipment and other cargo related to the drilling or other operations of the vessel.